Elevator systems of this kind are known, for example from European Patent Application EP-1 562 848 A1 The elevator system described there comprises two elevator cars in a common elevator shaft, with a respective drive and with a common counterweight. Each of the elevator cars has own sensors which enable determination of the position and the speed of the elevator cars. This document is regarded as closest state of the art.
It is disadvantageous with this known system inter alia that the safety of the entire system does seem to be given, but the elevator cars themselves are allocated data of a group control device. Moreover, the system appears to be relatively costly and difficult in operation.